Biol. Pharm. Bull. 29(2) 371—374 (2006)

due to increased bone resorption and reduced bone formation. The decrease in bone mass induces osteoporosis, which is widely recognized as a major public health problem. The most dramatic expression of this disease is represented by fractures of the proximal femur. Pharmacologic and nutritional factors may prevent bone loss with increasing age. Chemical compounds in food that act on bone metabolism, however, are poorly understood. Carotenoids are present in fruit and vegetables. Carotenoids have been shown to have a possible biological effect in cancer prevention. Retinol (vitamin A) is known to have a detrimental effect on bone at high doses. In laboratory animals, high levels of vitamin A lead to accelerated bone resorption, bone fractures, and osteoporotic bone lesions. b-Cryptoxanthin is a carotenoid that is abundant in Satsuma mandarin (Citrus unshiu MARC.) and it is enzymatically converted from b-carotene (provitamin A) in plants. Of the various carotenoids (including b-cryptoxanthin, lutein, lycopene, and b-carotene) and rutin (quercetin-3-rutinoside), b-cryptoxanthin has been found to have a unique anabolic effect on bone calcification in rat femoral tissues in vitro. Lutein, lycopene, b-carotene, and rutin had no effect on bone calcification in vitro. Moreover, b-cryptoxanthin has been shown to have a stimulatory effect on osteoblastic bone formation and an inhibitory effect on osteoclastic bone resorption in vitro. Oral administration of b-cryptoxanthin may have a preventive effect on bone loss with increasing age and on osteoporosis in vivo. Zinc, an essential trace element, has been shown to have a potent stimulatory effect on osteoblastic bone formation and an inhibitory effect on osteoclastic bone resorption in vitro. Oral administration of zinc compounds prevents bone loss in ovariectomized rats, an animal model of osteoporosis. Whether the combination of pharmacologic with nutritional factors exhibits an additive or synergistic effect on bone components has not been fully clarified. This knowledge may be important in preventing bone loss with increasing age. More recently, it has been shown that the combination of b-cryptoxanthin and zinc at relatively low doses can enhance the anabolic effects on bone components in rat femoral tissues in vitro. This study was undertaken to determine whether the combination of low-dose b-cryptoxanthin and zinc sulfate has anabolic effects on bone components in rats in vivo.